1. Technical Field
This invention relates generally to an improved bituminous binder composition useful with mineral aggregates to form roads and pavements, to serve as roofing materials, as pond lining materials and other uses where contact with moisture occurs. More particularly, the invention relates to a mixture of such a composition with mineral aggregates having improved resistance to damage from moisture and freeze-thaw cycling. The invention also relates to methods of providing areas surfaced with mixtures of such bituminous binder compositions and aggregate particles with improved weathering characteristics.
2. Background Art
Water or moisture often promote deterioration of asphaltic pavements by weakening the adhesive bond at the asphalt-aggregate interface. This deterioration is intensified by freeze-thaw cycling. Moisture damaged roads have low tensile strength and are easily cracked by the action of traffic. Roads that are located in areas where the temperature falls below the freezing point of water are prone to be severely damaged and cracked as the water or moisture present in any small cracks in the pavement composition freezes. Such damage tends to develop at the mineral aggregate-bituminous binder material boundary due to lack of adequate bonding or adhesion between the mineral aggregate and the bituminous material. Hence, asphalt pavements are particularly susceptible to damage during freeze-thaw cycling.
There are a number of known additives, or bond-improving agents, which are conventionally incorporated in bituminous compositions (asphalts) to improve adherence to aggregate surfaces. For example, secondary, tertiary and quaternary straight chain aliphatic amines serve as bond-improving agents. Such additives also include, for example, fatty acid amides of primary polyamines and their salts. Certain particularly useful fatty acid amides are set out in U.S. Pat. No. 2,950,211. Such amides include a fatty acid having a hydrocarbon chain with at least one substituent group that is connected to the hydrocarbon chain through a nitrogen atom.
While the compositions of the prior art are often effective in improving the bond between the bituminous binder composition and mineral aggregate particles, especially when the mineral aggregate particles are wet, they provide, at best, only a partial solution to the problems associated with moisture induced damage.
The present invention is directed to overcoming the problems as set forth above.
It is among the objects of this invention to provide additives or compositions for enhancing the weatherability of asphaltic-aggregate compositions.
It is another object of this invention to enhance the water damage resistance of asphaltic-aggregate compositions used as roads and other pavements, roofing materials, and pond lining materials.
Still another and more specific object of this invention is the improvement in resistance to damage from moisture and freeze-thaw conditions of asphaltic-aggregate compositions.
It is yet another object to provide a use for certain shale oil fractions having little or no uses.
Still a further object of this invention is to provide an economically feasible additive for enhancing the weatherability and general water damage resistance of asphaltic-aggregate composites.
Yet another object is to provide for an economic and environmentally acceptable method of disposing of portions of shale oil fractions.
Another object of this invention is to provide a method of enhancing weathering characteristics of asphaltic-aggregate compositions against moisture and particularly against freeze-thaw damage.
These and other objects will become apparent from the discussion found hereinafter.